The present disclosure relates generally to a method for displaying axial images and in particular, to a method for displaying axial images at varying slice thicknesses and interval values.
A medical imaging configuration, such as a computed tomography (CT) system can include an x-ray source that projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the “imaging plane.” The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements are acquired separately to produce a transmission profile.
CT systems can also include the x-ray source and the detector array being rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements i.e., projection data, from the detector array at one gantry angle is referred to as a “view”. A “scan” of the object comprises a set of views made at different gantry angles during one revolution of the x-ray source and detector.
In an axial scan, projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to as the filtered back projection technique. This process converts the attenuation numbers from a scan into integers called “computed tomography numbers” or “Hounsfield units”, which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
Slice thickness directly affects image resolution and scan efficiency. Typically, the optimal slice thickness will vary depending upon a variety of factors including the type of procedure being performed. Smaller slice thicknesses provide a more detailed image resolution than larger slice thicknesses. However, larger slice thicknesses are more efficient than small slice thicknesses since more of the region is scanned with a large slice thickness in a shorter period of time and larger slice thicknesses are easier to page through in order to find the slice that contains the area of interest. Typically, an operator selects a slice thickness prior to a scan to optimize scan efficiency and image quality based on a variety of factors including the type of procedure being performed.